1. Field of the Invention
The present invention relates to mechanical linkages which provide linear movement in response to temperature changes. More specifically, the present invention relates to improvements in thermal compensator mechanisms as employed in optical systems.
2. Description of the Prior Art
The problem of focus distortion in optical systems due to changes in temperature has been frequently discussed in the prior art. Generally, temperature variations cause glass lenses to expand or contract and vary the indices thereof. The lens mounts also tend to expand or contract due to changes in temperature and additionally affect the focal point. In order to maintain a fixed focal point throughout wide variations in temperature, many systems have been developed for compensating the above mentioned expansion and contraction.
In U.S. Pat. No. 1,325,936, compensation was achieved between two lenses by mounting each lens in separate mounting barrels and connecting the barrels at a point removed from the lenses. The two barrels were made of materials having different thermal coefficients of expansion, so that any change in temperature resulted in a separation change between the lenses corresponding to the difference between the two barrel expansions or contractions.
In U.S. Pat. No. 2,533,478, compensation was achieved by mounting the lenses in a barrel having a relatively low coefficient of expansion and connecting one end of the lens barrel to an expandable sleeve having a relatively high coefficient of expansion. The other end of the expandable sleeve was connected to an outer support sleeve having a relatively low coefficient of expansion.
In U.S. Pat. No. 2,537,900, compensation was achieved by mounting the lenses in a barrel having a relatively low coefficient of expansion and connecting one end of the lens barrel to a camera body. The camera body had a relatively high coefficient of expansion to vary the position of the focal point in compensating fashion to maintain the preset focus.